Cardiac Cycle Flashcards
Cardiac cycle duration
60(s)/heart rate (bpm)
Cardiac cycle
The sequence of electrical and mechanical events that leads to blood ejection from the heart
Systole
ventricular contraction (1/3)
Diastole
relaxation of ventricles (2/3)
Diastole
relaxation of ventricles (2/3)
End diastolic volume
volume of blood in ventricles at the start of systolic
End systolic volume
blood in heart after systole
Stroke volume
amount of blood pumped out of heart per beat
Ejection Fraction
stroke volume/end diastolic volume x 100
Stroke volume calculation
end diastolic volume - end systolic volume
Atrial systole
P wave
ventricles almost full - pressure gradient
atria contract to ‘top up’ volume in ventricle
4th heart sound
Isovolumetric contraction
start of QRS complex
interval between AV valves closing and semi lunar valves opening
contraction of ventricles - no change in volume
1st heart sound - closure of AV valves
LV contraction first - mitral valve closes first = split S1
Rapid ejection
opening of aortic/pulmonary valves
blood pumped out - volume in ventricles decreases
NO HEART SOUNDS
Reduced ejection
marks the end of systole
reduced pressure gradient = aortic/pulmonary valves close
flow from ventricles decreases + volume decreases more slowly
back flow causes semilunar valves to close
Isovolumetric relaxation
aortic and pulmonary valves shut - AV valves still shut until V pressure drops below A pressure
Dichrotic notch
atrial reassure continues to rise
aortic valve opens lasts and closes first = pressure - split S2
